Typically used laser devices are utilized in various fields. For example, as one of laser devices utilized as medical equipment, there are various optical medical imaging devices.
As such a medical imaging device, there is an optical coherence tomography (OCT) device and the OCT device may acquire a 3-dimensional image having high spatial resolution by using light coherence and capability of minute light concentration. However, the spatial resolution becomes rapidly degraded at a depth of 1 mm or longer due to strong scattering in a living tissue.
As a device for overcoming shortcomings of the OCT device having spatial resolution, there is a photoacoustic imaging device. A photoacoustic imaging device is a device in which high spatial resolution of an optical device and advantages of an acoustic imaging device less influenced by light scattering in a living tissue are combined. In order to obtain a photoacoustic effect, the photoacoustic imaging device requires a wavelength-variable laser having wavelengths strongly absorbed in a specimen. As such a wavelength-variable laser, there are an optical parametric oscillator (OPO) and a dye laser. However, since such a wavelength-variable laser is expensive and has a low pulse repetition rate of 20 kHz or less, it is difficult to obtain a high-speed real-time image.